This past year, we have discovered that the protozoan parasite, Toxoplasma gondii, enters host macrophages in two differing ways, by active invasion through the host cell membrane, and by phagocytosis. This coming year, we plan to extend these studies by analyzing the intracellular distribution of lysosomal enzymes in these parasitized macrophages to determine the fate of these toxoplasmas after the two differing mechanisms of cell ingress. Chronic granulomata will be produced in the lungs and peritoneal cavities of experimental animals, and the endocytosis of various soluble and particulate tracers will be examined. Subsequently, the localization of lysosomal enzymes will be studied with the aim of elucidating the intracellular pathways involved in enzyme production and transport to pinosomes and phagosomes.